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Abstract

Background

Despite a growing body of research from the United States and other industrialized
countries on the inverse association between supportive social relationships in the
school and youth risk behavior engagement, research on the measurement of supportive
school social relationships in Central America is limited. We examined the psychometric
properties of the Student Perceptions of School Cohesion (SPSC) scale, a 10-item scale that asks students to rate with a 5-point Likert-type
response scale their perceptions of the school social environment, in a sample of
public secondary school students (mean age = 15 years) living in central El Salvador.

Methods

Students (n = 982) completed a self-administered questionnaire that included the SPSC
scale along with measures of youth health risk behaviors based on the Center for Disease
Control and Prevention's Youth Risk Behavior Survey. Exploratory factor analysis was
used to assess the factor structure of the scale, and two internal consistency estimates
of reliability were computed. Construct validity was assessed by examining whether
students who reported low school cohesion were significantly more likely to report
physical fighting and illicit drug use.

Results

Results indicated that the SPSC scale has three latent factors, which explained 61.6%
of the variance: supportive school relationships, student-school connectedness, and student-teacher
connectedness. The full scale and three subscales had good internal consistency (rs = .87 and α = .84 for the full scale; rs and α between .71 and .75 for the three subscales). Significant associations were
found between the full scale and all three subscales with physical fighting (p ≤ .001)
and illicit drug use (p < .05).

Conclusion

Findings provide evidence of reliability and validity of the SPSC for the measurement
of supportive school relationships in Latino adolescents living in El Salvador. These
findings provide a foundation for further research on school cohesion and health risk
behavior in Latino adolescents living in the U.S. and other Latin American countries.

Background

Youth risk behavior is an important indicator of the health of young people based
on its association with several mortality and morbidity outcomes, including intentional
injury stemming from aggression and suicidal ideation, chronic disease resulting from
substance use and misuse, sexually transmitted disease, and undesired social outcomes
such as unintended teenage pregnancy [1]. While the social sciences may be far from identifying an immunization against harmful
behaviors connected to poor health outcomes, a growing body of literature in public
health points to the importance of the social context for its potential to confer
a protective effect against adverse health behaviors and health status. Supportive
interpersonal relationships within the school context may hold specific relevance
for protecting against a range of health risk behaviors among adolescents.

Psychosocial adolescent behavior theories such as social control [2] and social bonding theory [3], the Social Development Model [4], primary socialization theory [5], and resilience theory [6,7] highlight the important role of cohesive and supportive interpersonal relationships
within an adolescent's primary socialization contexts, including the school context,
for protecting against risk-taking behaviors. According to these theoretical perspectives,
the quality of affective relationships--and specifically caring and supportive relationships--that
one has with others contributes to the social bonds that subsequently reduce engagement
in risk-taking behavior.

Empirical research from industrialized countries has indicated a protective effect
of a supportive school environment and a student's connection to school on engagement
in various youth risk behaviors. Social bonding of students, student school-connectedness,
and a caring and supportive school climate have been found to be inversely associated
with substance use and delinquency [8-12], aggression [10,11,13], sexual risk behavior [9,13], and depressive symptoms and suicidality [10,12,13]. In a four-year randomized controlled trial with 25 secondary schools in Australia,
a school-based intervention designed specifically to promote social inclusion and
commitment to education was found to significantly reduce risk behavior in adolescents,
including substance use and early initiation of sexual intercourse [14].

Although past theoretical and empirical research provide strong evidence for the association
between supportive school social climate and student-school connectedness with youth
risk behaviors, several gaps in the literature remain. For example, some studies conceptualize
supportive school relationships at the individual level in terms of a student's direct
connection to school and the people within school [10], while other studies conceptualize social relationships at an ecological or contextual
level in terms of a general school climate of caring and supportive relationships
[8,15,16]. Measures that capture both individual-level connection to school as well as a contextual
level of supportive climate are needed. On a related note, some research has found
that different dimensions of school connectedness, such as connectedness with teachers
vs. general connectedness with school, have different associations with the initiation
of youth risk behavior such as substance use [13]. The development of measures that distinguish between levels and dimensions of social
relationships within the school context may contribute to a better understanding of
direct and indirect social influences on health behavior. Lastly, published research
on the validity and reliability of instruments purporting to measure supportive school
relationships with Central American adolescent populations is limited. Because Central
American adolescents share many of the same risk behaviors as U.S. adolescents, such
as drug use [17] and aggressive behavior such as physical fighting [18,19], research on the protective effects of specific social contexts such as schools holds
the potential to guide intervention efforts for reducing youth risk behavior initiation
in Central American youth.

To assess the associations between supportive school relationships and youth risk
behaviors among Central American youth, it is important to construct valid and internally
consistent measures of supportive school relationships that encompass both individual-level
and contextual-level items, and to evaluate the measure with the intended target population.
In contributing to the measurement of supportive school relationships in Central America,
the current study examined the psychometric properties of the Student Perceptions of School Cohesion scale with a sample of public secondary school students living in the central region
of El Salvador. The specific aims of the current study were to: 1) explore the factorial
structure of the Student Perceptions of School Cohesion scale and determine if one
or more latent factors characterized the set of scale items; 2) examine the internal
consistency reliability of the scale(s); and 3) assess evidence of construct validity
of the scale(s) by exploring the association between supportive school relationships
and selected youth risk behavior outcomes.

Method

Instrument

The study is based on survey data collected as part of the Salud y Bienestar de los Jóvenes en El Salvador study [Health and Wellbeing of Youth in El Salvador]. The Salud y Bienestar de los Jóvenes self-administered questionnaire consisted of 66 closed-ended items with dichotomous
and ordinal-level response choices to assess perceptions of school social environment
and health risk behaviors among Salvadoran secondary school students. Ten items of
the Salud y Bienestar de los Jóvenes questionnaire specifically assessed student perceptions of school cohesion and student-school
connectedness. The current study focuses on these ten items with the aim of evaluating
their psychometric scale properties. The ten Student Perceptions of School Cohesion [SPSC] items asked students to rate with a 5-point Likert-type response scale how
strongly they agree or disagree with statements such as: "People care about each other
in this school," "Students in my class work together to solve problems," and "Students
and teachers at this school are close with each other" (see Table 1 for a full list of items). In the Salud y Bienestar de los Jóvenes questionnaire, the ten items were formatted under two consecutive questions, with
the first six items in Table 1 grouped under one question and the remaining four items grouped under a separate
question. The ten items were based in part on items from Battistich's and Hom's [8] "Students' sense of the school as a community" subscale of caring and supportive
interpersonal relationships as well as items measuring student-school connectedness
from the National Longitudinal Study on Adolescent Health [10].

Table 1. Item-total correlation and response distribution of Student Perceptions of School
Cohesion scale among Salvadoran public secondary school students (n = 935)

All items measuring youth risk behaviors were selected from the instrument used for
the U.S. Youth Risk Behavior Survey [20], a comprehensive adolescent health survey that has been administered biennially in
the United States since 1991 by the Centers for Disease Control and Prevention. The
current study examined two risk behaviors in relation to the SPSC scales to assess
construct validity: aggressive behavior (physical fighting in the past 12 months)
and illicit drug use (ever having consumed cocaine, marijuana, or inhalants). These
risk behaviors were selected based on their associations in previous studies with
student-school connectedness and supportive school climate [8-12,21]. Risk behaviors were coded as present/absent. In assessing the associations between
the SPSC and risk behaviors, we took into account the following student demographic
characteristics: gender, age, geographic location (urban/rural), and subjective economic
status. Gender, age, and subjective economic status were determined based on self-reported
measures; geographic location was determined according to school classifications from
the Ministry of Education of El Salvador. Subjective economic status was adapted from
a measure used in previous research with high school students [22] that asks students to rate their family's standard of living on a 5-point response
scale, with 1= living very well off to 5 = poor.

All items were translated from English to Spanish and back-translated and centered
with the assistance of two Salvadoran university students and a native English speaker
fluent in Spanish. Content and face validity were assessed through discussions with
national directors from the Ministry of Education of El Salvador and school principals
to evaluate the appropriateness and relevance of the items within the Salvadoran school
context. In order to assess the level of comprehension of the items, the questionnaire
was pilot-tested with a separate sample of 35 urban eighth grade students attending
a school in the study area. This pilot sample was not included as part of the main
study sample.

Sample and Data Collection

A multistage sampling frame was employed in which school districts, schools, and classrooms
were randomly selected. Participants included eighth and ninth grade secondary school
students attending 16 public schools in the central region of El Salvador who were
present on the day of the study. The questionnaire was administered to students between
June and August of 1999 according to standardized data collection procedures by a
team comprising a technician from the National Training Center of the Ministry of
Education of El Salvador, a Salvadoran university student, and the first author.

Student informed assent and parental informed consent were obtained for all participants
prior to participation in the study, and collection of information was conducted in
a confidential manner. Student assent was obtained by providing a verbal and written
description of the study to all potential participants, which detailed the subject
matter and placed specific emphasis on the study's voluntary and confidential nature.
Under the informed assent procedure, students were informed that if they did not participate
in the study, neither their grades in school nor their standing in school would be
affected. Furthermore, students were informed that they did not have to answer any
question they did not want to answer, that they could stop participating in the survey
at any time, and that they would be provided an alternative activity if they did not
want to participate in the survey. In addition to obtaining student assent for participation
in the study, passive parental informed consent for participation in the study was
obtained for all participants. At the time of the research, passive parental informed
consent was an accepted protocol of the United States Centers for Disease Control
and Prevention (CDC) in Atlanta, Georgia, for conducting research with adolescents
in their Youth Risk Behavior Survey (YRBS), a national monitoring tool for assessing health risk behavior trends [20]. This consent procedure consists of sending a letter home with the student that describes
the study and asks parents or guardians to submit a signed form only if they do not
wish their child to participate in the study. In ensuring confidentiality of the participants,
the survey was administered by trained data collectors who followed protocols that
included separation of desks during the completion of the surveys as well as close
monitoring of students during the completion of the survey. Names of participants
and schools were not included on questionnaires nor connected in any way with questionnaire
responses. The study protocol, along with the study objectives, methods, and English
language version of the questionnaire, were reviewed and approved by the Committee
for the Protection of Human Subjects of the University of Texas Health Science Center
at Houston; the Spanish translation of the study objectives, methods and questionnaire
were reviewed and approved by a team composed of Salvadoran parents and representatives
of the Ministry of Education of El Salvador that was formed specifically to ensure
the ethical conduct of the study as well as the protection of study participants.

Data Analysis

To assess the dimensionality of the Student Perceptions of School Cohesion scale, an exploratory factor analysis was conducted. We used principal axis analysis
in SPSS version 15.0 (Chicago, Il.) as the extraction method. Based on the relatively
high correlations among the majority of items (> .3), an oblique rotation was performed
using Promax. Three criteria from Green and Salkind [23] were applied to determine the number of factors to be retained: 1) the absolute values
of the eigenvalues; 2) the relative values of the eigenvalues; and 3) the relative
interpretability of the rotated solutions. In addition, a scree plot and the variance
explained by the factor solution also were considered in making decisions to retain
or exclude factors.

Two internal consistency estimates of reliability were computed for the Student Perceptions
of School Cohesion scale: a split-half coefficient expressed as a Spearman-Brown corrected
correlation and Cronbach's α. For the split-half coefficient, the scale was split
into two halves by odd and even numbering of items with the goal of creating equivalent
halves. The following criteria were used to evaluate coefficient α: α > 0.60 reflects
modest internal consistency and α > 0.70 reflects good internal consistency for research
purposes [24].

This study also assessed the construct validity of the scale(s). Construct validity
is concerned with the theoretical relationship of a variable with other variables
[25]. Adolescent psychosocial theories such as social control and bonding theories [2,3] and the Social Development Model [4] posit that weak bonds of attachment with conventional forms of society such as the
school result in increased health risk and delinquency behaviors. In addition, an
emerging body of empirical research has suggested that supportive school environment
and social bonding among students at school are inversely related to several youth
risk behaviors such as aggressive behavior and substance use [8-10].

Based on this theoretical and empirical foundation, and with the aim of assessing
construct validity of SPSC scale(s), the SPSC scale scores were examined for their
association with participation in physical fights in the past 12 months and lifetime
illicit drug use. A composite variable was created for each of the subscales that
was dichotomized according to strength of agreement with school cohesion statements,
with high school cohesion defined as those who responded 'strongly agree' and 'somewhat
agree' and low school cohesion defined as 'neutral', 'somewhat disagree', and 'strongly
disagree'. Multiple logistic regression analyses were conducted to assess whether
students who reported high school cohesion were significantly less likely to report
physical fighting and illicit drug use than students who reported low school cohesion,
adjusting for gender, age, urban/rural geographic location, and subjective economic
status. Differences were considered statistically significant if the p value was <
.05.

Results

Among 1007 public school students present on the day of the questionnaire administration,
17 opted not to participate in the study and 8 students provided invalid or inconsistent
responses (e.g., 'never smoked' and then responded 'smoked 20 or more times'), resulting
in a total sample size of 982 completed questionnaires for analysis. The mean age
of the respondents was 15 years (SD ± 1.4), and the sample had a slightly higher proportion
of male students (52.6%).

Descriptive Statistics

Item-by-item descriptive analyses of the SPSC scale indicate that responses were skewed
toward more favorable perceptions of school cohesion (Table 1). Between 72% and 92% of the sample indicated a response of 'strongly agree' or 'somewhat
agree' with the school cohesion items, with "people care about each other in this
school" receiving the lowest favorable rating and "I feel a part of this school" receiving
the highest rating.

Exploratory Factor Analysis

Although "Kaiser's rule" suggests that only components with eigenvalues greater than
one should be retained [26], this criterion may be too restrictive and may fail to identify potential factors.
Results of this study indicated that eigenvalues for two of the ten components were
greater than 1 (4.15 and 1.08), and one of the components approached 1 (.928). These
three components accounted for a total of 61.6% of the variance, of which the third
component explained 9%. The scree plot also suggested the presence of three separate
factors before tapering off, indicating that the initial hypothesis of unidimensionality
was incorrect. Based on the size of the eigenvalues, the variance explained, and the
scree plot results, three factors were retained and rotated using Promax rotation.
The correlations (factor loadings) of items in the final three factor model are reported
in Table 2. These factors are interpretable from both a conceptual and theoretical basis. Factor
1, supportive school relationships, includes items that reflect supportive relationships at an ecological or contextual
level, which may not reflect an individual's direct connection to that supportive
context (Table 1). Subscale items include both peer and general social relationships at school. Factor
2, student-school connectedness, includes items that are representative of a student's direct connection to the overall
school and to the people within the school. Lastly, Factor 3, student-teacher connectedness, represents emotional closeness between students and teachers at an ecological or
contextual level.

Table 2. Correlations between the School Cohesion items and School Cohesion factors in a secondary
school from central El Salvador (n = 935)

Internal Consistency Reliability

The two internal consistency estimates of reliability computed for the Student Perception
of School Cohesion scale provided similar results. For the "Supportive School Relationships"
subscale, the values computed from the Spearman-Brown corrected correlation and coefficient
alpha were .71 and .74, respectively. For the "Student-School Connectedness" subscale,
the Spearman-Brown corrected correlation and coefficient alpha were .75 and .72, respectively.
Lastly, for the "Student-Teacher Connectedness" subscale, the coefficient alpha was
.72, which is equivalent to the Guttman-Flanagan split half; the Spearman-Brown coefficient
was not calculated based on the presence of only two items. For the full scale, Spearman-Brown
corrected correlation and coefficient alpha were .87 and .84, respectively. These
values indicate good internal consistency.

Construct Validity

Composite variables were created for each subscale identified in the exploratory factor
analysis to assess potential evidence of construct validity of the SPSC subscales
as per their associations with two adolescent risk behavior variables. The supportive
school relationships and student-school connectedness composite variables ranged from
4 to 20 and were dichotomized according to strength of agreement, with 4 to 8 (high
support/connectedness) equal to 'strongly agree' or 'somewhat agree' and 9 to 20 (low
support/connectedness) equal to 'neutral', 'somewhat disagree', and 'strongly disagree'.
The student-teacher connectedness variable ranged from 2 to 10, with high connectedness
equal to 2 to 4 and low connectedness equal to 5 to 10.

Table 3 presents the associations of perceived school social cohesion with physical fighting
and illicit drug use. In exploring the association between the full scale and the
risk behavior outcomes, students with high perceptions of school social cohesion were
significantly less likely to report both physical fighting in the last 12 months (Adjusted
Odds Ratio (AOR) = 0.50, 95% Confidence Interval (CI): 0.35, 0.73, p < .001) and lifetime
illicit drug use (AOR = 0.34, 95% CI: 0.20, 0.57, p < .001). We found the three supportive
social relationship subscales had a similar protective effect on physical fighting.
Student who reported high perceptions of supportive school relationships, student-school
connectedness, and student-teacher connectedness were significantly less likely to
report engagement in a physical fight in the past 12 months (AOR = 0.56, 95% CI: 0.41,
0.78; AOR = 0.49, 95% CI: 0.33, 0.75; and AOR = 0.54, 95% CI: 0.37, 0.79, respectively,
p ≤ .001). In assessing the associations between the composite variables and illicit
drug use, students with high perceptions of supportive school relationships reported
significantly less illicit drug use (OR = 0.48, 95% CI: 0.29, 0.77, p = .001). Less
robust but still significant inverse associations were found for illicit drug use
with student-school connectedness (OR = 0.47, 95% CI: 0.26, 0.84, p = .01) and student-teacher
connectedness (OR = 0.55, 95% CI: 0.32, 0.95, p = .03) (Table 3).

Table 3. Percentage of public secondary school students from central El Salvador who reported
engaging in a physical fight and illicit drug use by level of perceived social cohesion
within school and student-school connectedness. (n = 935)

Discussion

Although several efforts have been made to develop instruments to measure quality
of life and well-being of students within schools [8,27-29], few studies have examined well-being as related to school social relationships in
a Central American school context. This study explored the psychometric properties
of the Student Perceptions of School Cohesion [SPSC] scale -a scale that focuses specifically
on student connectedness and caring and supportive social relationships within the
school context--based on a sample of public secondary school students living in the
central region of El Salvador. Findings from this study indicated that the SPSC scale
has three latent factors related to supportive school relationships, student-school connectedness, and student-teacher connectedness and that these subscales as well as the full SPSC scale have good internal consistency.
The construct validity of the SPSC scale is further strengthened by the observed associations
between school social environment and youth risk behaviors found with the full scale
and all three subscales with physical fighting and illicit drug use.

The three factors identified in the rotated solution, supportive school relationships,
student-school connectedness, and student-teacher connectedness, are interpretable
from both a conceptual and theoretical basis. Items for the first factor stem from
Battistich's and Hom's [8] "Students' sense of the school as a community" subscale of caring and supportive
interpersonal relationships, which provides a more ecological measure of school climate.
In addition to empirical findings of the importance of supportive school social relationships
at an ecological level for reducing risk behaviors such as drug use and delinquency
[see [8,9]], this contextual level of social cohesion, with or without direct individual-to-school
ties, may provide a sense of social belongingness for adolescents. Perceptions of
social belongingness, even in the absence of direct interpersonal social ties, have
been cited by sociological theorists as important for psychological well-being [30].

Our findings on the remaining SPSC scale items, which stem from research on school
connectedness [10], indicate that these items represent two different latent factors: student-school
connectedness and student-teacher connectedness. A student's level of connectedness
to school has been found to be protective against a range of youth risk behaviors
[10-12,21]. The distinction of student-school connectedness and student-teacher connectedness
may be important given findings by McNeely and Falci [13] that indicated a protective effect of teacher support on adolescent risk behavior
but no effect of student connectedness to school. Our research also indicates that
supportive social relationships at school represents a multidimensional construct
that may differ in terms of school relationships at an ecological or contextual level,
a student's direct connection to the school and people within the school, and a student's
connection to his/her teacher.

Findings of the current study provide some evidence of construct validity for the
use of the Student Perceptions of School Cohesion scale in measuring supportive school
social relationships. Our findings of an inverse relation between the subscale of
supportive school relationships and aggression mirror findings from Battistich and
Hom [8] in their study of fifth and sixth graders in the United States. We also found inverse
associations between student-school connectedness and student-teacher connectedness
and aggression- findings supported by previous research [10,13,31]. The observed associations between the full SPSC scale and the supportive school
relationships subscale and illicit drug use are also similar to findings by McBride
et al. [9] regarding higher student social bonding at school and lower illicit drug use.

Several possible explanations may account for the less robust but still significant
associations found between the student-school connectedness and student-teacher connectedness
with illicit drug use. First, the illicit drug use measure was based on lifetime drug
use; therefore, this measure may not have been specific enough to capture the influence
of school connectedness on this behavior. Distinguishing between heavy drug users
and experimental drug users might provide more information about the influence of
school relationships on illicit drug use. Second, it is possible that the different
levels and forms of social relationships at school may affect drug use differently.
Feeling connected or not connected to classmates and teachers may be less important
for drug use than perceiving supportive relationships within the broader school context,
as suggested in this study. As such, students who perceive low support in the school
environment, despite their individual connection to school, may seek out relationships
outside of school to fill a social connectedness void. Lightfoot's [[32], p.10] qualitative research on adolescents and risk taking suggests that adolescents
engage in risk behaviors with peers as a way of promoting cohesion, trust, and closeness
in initiating new relationships and consolidating existing relationships. Engaging
in substance use with peers may be one approach for developing connectedness with
other adolescents when social connectedness is not perceived within the school environment.
As evidence is mixed for the association between student-school connectedness and
illicit drug use, with some studies finding a positive association [12] and others finding no association [13], further research on the dimensions of school connectedness and their association
with drug use is warranted.

Limitations and Future Research Directions

Some limitations of the scale are worth noting. For example, as 72% to 92% of the
responses fell within the first two response categories, the SPCS scale may be strengthened
by expanding the response scale to capture more variance on the social relationship
and school connectedness items. As this study was limited to measuring general social
support, the scale may be enhanced by further conceptualizing and operationalizing
support within the school environment, such as instrumental, motivational, and emotional
support [33,34]. Improved operationalization of social support would allow researchers to explore
which types of support within the school environment are most important for preventing
or reducing selected youth risk behaviors. Distinguishing between the source of social
support--be it teacher, classmate, or friend--within the scale may also provide further
insights into the social relationships that are most important for protecting against
health risk behavior. As this study found that student-teacher connectedness may be
a separate factor from student-school connectedness, the scale may be strengthened
by including additional measures of the student-teacher relationship, such as fair
treatment of students by teachers or personal interest of teachers in how the student
is doing [see [29]]. Further research on the validity of the SPSC is also warranted given that our study
focused only on two risk behavior outcomes that may be relatively distal to the construct
under measurement. Future research on the test-retest reliability of the scale would
also provide further understanding of the temporal stability of the measure.

Other limitations that should be considered include the cross-sectional study design
for assessing associations with youth risk behavior, which limits our ability to assess
causality. Future research is needed to assess both the causal role of school social
cohesion in reducing risk behavior in Latin American contexts as well as the mediated
pathways between social cohesion and youth risk behavior. Our measures were based
on self-report, which may be prone to recall bias as well as social desirability bias
in the reporting of risk behaviors and social connectedness. We should also note that
the study was limited to those students who were present on the day of the survey.
Because the study did not account for truant students, risk behavior prevalence estimates
may have been underestimated and the generalizability of the findings to those students
is limited. Lastly, further research is needed to expand the tests for reliability
and validity of the scale with students from other age groups as well as other Latin
American and U.S. Hispanic populations.

Conclusion

Although a growing body of empirical research, including several adolescent psychosocial
theoretical perspectives, points to the importance of the school social environment
for influencing both health-promoting and health-debilitating behavior, achieving
a more complete understanding of the associations between school social environment
and health-risk and health-enhancing behavior among adolescents will require the development
of instruments with evidence of strong validity and reliability to measure the school
environment. Findings from this study suggest that the Student Perceptions of School
Cohesion scale may be a useful instrument for measuring supportive school social relationships
and connectedness within a Central American population. The strengths of this scale
include: 1) its parsimonious structure based on only 10 items, 2) a 3-factor structure
that represents the contextual-level supportive school social climate and individual-level
student-school and student-teacher connectedness dimensions of supportive social relationships
in school that have been found to be associated with adolescent risk behavior, 3)
good internal consistency for the full scale and subscales, and 4) evidence of construct
validity based on a large sample of public secondary school students in El Salvador.

Competing interests

The authors declare that they have no competing interests.

Authors' contributions

AES and MR conceived of the original study and overall design of the study. AES was
responsible for the overall preparation of the manuscript, including the analysis
and write-up of the findings and discussion. AM contributed to the drafting and review
of the analysis and results section. GQ, MA, and MR provided critical review and revision
of the manuscript. All authors read and approved the final manuscript.

Acknowledgements

The authors are thankful for the insightful comments received from Dr. Paul Swank,
Professor-Department of Pediatrics, University of Texas Health Science Center-Houston,
who provided critical review of earlier drafts of this manuscript. The authors also
acknowledge the logistical support received for the original study upon which these
data are based from Lic. Lesvia Salas and Lic. Rosa Luz Vega from the Ministerio de
Educación, Centro de Capacitación in San Salvador, El Salvador. Preparation of this
manuscript was made possible in part by the Michael & Susan Dell Foundation support
of Dr. Springer's faculty position at the University of Texas School of Public Health-Austin
as well as the National Cancer Institute/NIH Grant #2R25CA57712-11 that funded Dr.
Springer's Postdoctoral Fellowship, Cancer Prevention and Control Training Program
in the Center for Health Promotion and Prevention Research, University of Texas-Houston
School of Public Health.